Hydrocarbon blowing agents such as pentane and cyclopentane are considered viable alternatives to the traditional CFC's in the rigid foam insulation sector. A publication by H. Ballhaus et al. entitled "Hydrocarbons Provide Zero ODP and Zero GWP Insulation for Household Refrigeration," in Polyurethanes World Congress 1993, Oct. 10-13, 1993, pages 33-39, describes a foaming apparatus adapted for use with the volatile hydrocarbon blowing agents. As can be seen from the description in this publication, the hydrocarbon is separately metered into the mix head, or fed into a day tank which is kept under constant agitation. Many of the insulation foams use polyester polyols as the base polyol. The hydrocarbons have only a limited or no solubility in most polyester polyols. To avoid phase separation, the hydrocarbon blowing agent must either be metered into a high pressure mix head, or fed into the day tank under agitation to keep the hydrocarbon mixed with the polyol.
Therefore, we found it desirable to find a chemical agent which would keep hydrocarbon blowing agents dispersed throughout the polyol in the absence of agitation, either in the form of an emulsion, a suspension, or homogeneously solubilized. The chemical agent chosen, however, should not sacrifice the mechanical properties of an equivalent foam made in the absence of the chemical agent, in particular, the k-factor, the flammability, the compressive strength, and the dimensional stability of the foam.